1. Field of the Invention
The present invention relates to aliphatic polyesters, to methods for manufacturing aliphatic polyesters, and to methods for recycling cellulose.
2. Description of the Related Art
Celluloses in an amount of 109 to 1011 tons are produced annually and are widely used for structural materials, filling agents, food additives, adhesives, and the like. However, in recent years, concomitant with the larger use of celluloses, the amount of waste celluloses has also increased.
As techniques of decomposing celluloses for recycling, for example, a method for producing hydrocarbons, such as methane or ethane, from celluloses is disclosed in Japanese Unexamined Patent Application Publication No. 5-213778, and a method for producing alcohols from celluloses by using microbial action is disclosed in Japanese Unexamined Patent Application Publication No. 11-299479.
In view of recycling waste celluloses, through research on the techniques described above carried out by the inventor of the present invention, it was found that a novel technique must be developed which can efficiently recycle waste celluloses in order to overcome the problem of an increasing amount of waste cellulose year by year.
In consideration of the problem described above, by intensive research and development by the inventor, a novel method was found for synthesizing an aliphatic polyester, which had a relatively high molecular weight and thereby could be used instead of conventional plastic products, from gluconolactone which is obtained from cellulose via D-glucose, whereby the present invention was made. In addition, the novel method described above ensures efficient recycling of waste celluloses, and in other words, production of high quality plastics can be achieved by using celluloses as starting materials.
Accordingly, an object of the present invention is to provide a novel aliphatic polyester produced by using celluloses as a starting material and to provide a method for recycling celluloses.
Another object of the present invention is to provide an aliphatic polyester represented by the formula (I) shown below. 
In the formula (I), R represents a hydrogen atom, an acetyl group, or a linear or a branched alkyl group having 1 to 3 carbon atoms. In addition, the subscript n represents an integer of 10 to 6,000.
Another object of the present invention is to provide a method for manufacturing an aliphatic polyester represented by the formula (I) shown below, comprising a step of performing ring-opening polymerization of gluconolactone represented by the formula (II) shown below. 
In the formula (I), R represents a hydrogen atom, an acetyl group, or a linear or a branched alkyl group having 1 to 3 carbon atoms. In addition, the subscript n represents an integer of 10 to 6,000. 
In the formula (II), R represents a hydrogen atom, an acetyl group, or a linear or a branched alkyl group having 1 to 3 carbon atoms.
Another object of the present invention is to provide a method for manufacturing an aliphatic polyester represented by the formula (I) shown below, comprising a step (i) of forming D-glucose by hydrolyzing cellulose, a step (ii) of forming gluconolactone represented by the formula (II) shown below from the D-glucose, and a step (iii) of performing ring-opening polymerization of the gluconolactone. 
In the formula (I), R represents a hydrogen atom, an acetyl group, or a linear or a branched alkyl group having 1 to 3 carbon atoms. In addition, the subscript n represents an integer of 10 to 6,000. 
In the formula (II), R represents a hydrogen atom, an acetyl group, or a linear or a branched alkyl group having 1 to 3 carbon atoms.
Another object of the present invention is to provide a method for recycling celluloses, comprising a step (i) of forming D-glucose by hydrolyzing cellulose, a step (ii) of forming gluconolactone represented by the formula (II) shown below from the D-glucose, and a step (iii) of performing ring-opening polymerization of the gluconolactone so as to form an aliphatic polyester represented by the formula (I) shown below. 
In the formula (II), R represents a hydrogen atom, an acetyl group, or a linear or a branched alkyl group having 1 to 3 carbon atoms. 
In the formula (I), R represents a hydrogen atom, an acetyl group, or a linear or a branched alkyl group having 1 to 3 carbon atoms. In addition, the subscript n represents an integer of 10 to 6,000.
In this connection, lactones are compounds having intermolecular cyclic ester structures, and some lactones are formed into aliphatic polyesters by open-ring polymerization. The aliphatic polyesters thus formed are used for various industrial applications, such as plastic molded products, films, hot-melt adhesives, and the like. As lactones to be used as starting materials for aliphatic polyesters, for example, xcex5-caprolactone, xcex4-valerolactone, and butyrolactone are known. However, an aliphatic polyester formed by open-ring polymerization of the gluconolactone represented by the formula (II) described above is the first polymeric compound synthesized by the inventor, and hence, the aliphatic polyester represented by the formula (I) is a novel polymeric compound.
According to the present invention, an aliphatic polyester having a high molecular weight can be manufactured by performing a ring-opening polymerization of gluconolactone formed from cellulose via D-glucose, and since the characteristics of mechanical strengths and the like are sufficiently superior, the aliphatic polyesters described above can be used as plastic molded products.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.